|Pos|Driver|Entrant|Constructor|Time/Retired|Grid|
|---|---|---|---|---|---|
|1|Innes Ireland|Team Lotus|Lotus-Climax|1.00:14.8|4|
|2|Stirling Moss|Rob Walker Racing Team|Cooper-Climax|+ 2.8 s|2|
|3|Chris Bristow|Yeoman Credit Racing Team|Cooper-Climax|+ 1:05.0 s|1|
|4|Bruce McLaren|Cooper Car Company|Cooper-Climax|+ 1:17.6 s|6|
|5|Graham Hill|Owen Racing Organisation|BRM|41 laps|9|
|6|Jo Bonnier|Owen Racing Organisation|BRM|41 laps|10|
|7|Tony Brooks|G.A. Vandervell|Vanwall|41 laps|8|
|Ret|Roy Salvadori|C.T. Atkins / High Efficiency Motors|Cooper-Climax|Transmission|5|
|Ret|Harry Schell|Yeoman Credit Racing Team|Cooper-Climax|Throttle|3|
|Ret|Mike Taylor|Taylor & Crawley|Lotus-Climax|Engine|13|
|Ret|Keith Greene|Gilby Engineering|Cooper-Climax||12|
|Ret|Alan Stacey|Team Lotus|Lotus-Climax|Oil pipe|11|
|Ret|Dan Gurney|Owen Racing Organisation|BRM|Accident|7|
|WD|Jack Brabham|Cooper Car Company|Cooper-Climax||-|
|WD|Geoff Richardson|Geoff Richardson|Cooper||-|

Question: how many drivers participated in the 8th glover trophy race?
Answer: 15